Fluid couplings, such as the type commonly found on the end of flexible hoses often use ball valves. The flow passage of a coupling or fitting houses the ball valves. Rotating 90.degree. fully opens or closes the valves. Closing the ball valves before disconnecting the coupling provides low spillage or zero spillage of fluid, typically a hydrocarbon. When the couplings join together, each ball valve rotates to a position which permits flow. Before the couplings separate, each ball valve rotates to a flow preventing position. The ball valves interfit with one another so that a minimum volume of fluid is lost when the couplings separate.
One improvement in ball valve design has been a semi-spherical depression in one ball valve with the other ball valve resting in the depression. This is a concave/convex ball valve design. Another improvement is a coupling that reduces spillage to less than 1 mL. In addition, the coupling provides numerous safeguards against spillage. The handle design prohibits incorrect sequencing of the ball valves during opening and closing. Another feature of the ball valves is an interlocking means which prevents the coupling from being disconnected until both valves are fully closed. The convex ball must be opened first by turning the ball 90.degree.. The concave ball then can be opened. Closing the valves require turning the concave ball first, then turning the convex ball, Handles are designed to prohibit wrong sequencing of opening and closing. Each handle also includes redundant safety locks which prevent the valve from opening when the valve halves are uncoupled.